{
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\begin{tabular}{l*{6}{c}}
\hline\hline
          &\multicolumn{1}{c}{(1)}&\multicolumn{1}{c}{(2)}&\multicolumn{1}{c}{(3)}&\multicolumn{1}{c}{(4)}&\multicolumn{1}{c}{(5)}&\multicolumn{1}{c}{(6)}\\
          &\multicolumn{1}{c}{ProtectEnvir}&\multicolumn{1}{c}{ProtectEnvir}&\multicolumn{1}{c}{ProtectEnvir}&\multicolumn{1}{c}{ProtectEnvir}&\multicolumn{1}{c}{ProtectEnvir}&\multicolumn{1}{c}{ProtectEnvir}\\
\hline
main      &                  &                  &                  &                  &                  &                  \\
Strong\_FTR&   -0.309\sym{*}  &   -0.185         &   -0.185         &   -0.185\sym{**} &   -0.554\sym{***}&   -0.112         \\
          &  (0.157)         &  (0.135)         &  (0.147)         &  (0.058)         &  (0.148)         &  (0.121)         \\
\hline
\(N\)     &    64666         &    64666         &    64666         &    64666         &    64666         &    64666         \\
prob      &                  &                  &                  &    0.095         &                  &                  \\
\hline\hline
\multicolumn{7}{l}{\footnotesize Standard errors in parentheses}\\
\multicolumn{7}{l}{\footnotesize \sym{*} \(p<0.05\), \sym{**} \(p<0.01\), \sym{***} \(p<0.001\)}\\
\end{tabular}
}
